The water saving is required in many settings including ordinary homes and in commercial facilities. One of the water saving methods is attaching a water saving disc to the water delivery devices such as a water tap. The water saving disc in the prior art is attached to the water delivery devices by installing the pillar-shaped disc inside of the water tap. The amount of the water flow is decreased by narrowing the water flow diameter with the water saving disc even if the opening diameter of the water tap is large.
For example, the basic shape of the conventional water saving disc is a pillar-shape corresponding to the cylindrical water pipe and the through-hole penetrates from the upper surface to the lower surface of the pillar-shape water saving disc. When installing such a conventional water saving disc to the water tap, the amount of the running water is decreased because the passage of the water flow is limited to the through-hole whose diameter is less than that of the water tap, so the water saving is achieved. The number of the through-hole is not limited to one, and two or three through-holes can be arranged in the conventional water saving disc.
For example, the conventional water saving disc described in the JP H09-095985 comprises a pillar-shaped water saving disc and at least three through-holes formed through from the upper surface to the lower surface. These through-holes can have a certain skew relative to each other. For example, the distance between the through-holes on the upper surface is small, and the distance between the through-holes on the lower surface becomes large corresponding to its height. In general, the large flange is formed on the upper surface edge, so the conventional water saving disc can be installed in the water tap. Three through-holes are formed through the water saving disc, and these though holes are arranged in a concentric circle.
Generally speaking, there are certain needs to make so-called bubble foam water from the normal tap water by aeration. In the prior art, there are several conventional water saving discs that include the aeration mechanism. The conventional aeration mechanism utilizes the side hole formed in the side wall for aerating the outer air into the water flow running in front of the hole. In this conventional aeration mechanism, only a small amount of air can be aerated to the water flow and an insufficient quality level of the bubble foam water is obtained.                Prior art 1: JP H09-095985        Prior art 2: JP 2000-104300        Prior art 3: JP Utility model 3114347        